The present invention relates to a new and useful process for producing hemiketals and hemithioketals. More particularly, the present invention relates to a process for producing certain hemiketals and hemithioketals useful in manufacturing alkyl 4,4,4-trifluoroacetoacetate or thioalkyl 4,4,4-trifluoroacetoacetate.
As part of their chemical structure, many agriculturally and pharmaceutically active compounds contain at least one trifluoromethyl functional group. The presence of one or more such groups in the compounds contributes to the desired activity of the compounds. In U.S. Pat. No. 4,785,129, compounds of alkyl 4,4,4-trifluoro-3-oxo-butanethioates, which are also referred to as thioalkyl trifluoroacetoacetates, are disclosed, along with the fact that methyl and ethyl esters of 4,4,4-trifluoro-3-oxo-butanoic acids are commercially available compounds. It is also disclosed in that patent that such compounds are useful intermediates for the preparation of herbicidal pyridine dicarbothioates and herbicidal pyridine dicarboxylates.
In U.S. Pat. No. 4,618,679, the preparation of herbicides using a 3-ketoester and suitable aldehydes as intermediates is disclosed.
Various processes for making trifluoroacetoacetic acid compounds are known. For example, U.K. specification No. 931,689 discloses the manufacture of fluorinated acetoacetic acid chlorides, wherein a fluorinated acetyl chloride is reacted with ketene, desirably in the presence of a suitable solvent.